This invention pertains generally to the conversion of signals from analog to digital form and, more particularly, to a system and method for extending the dynamic range of an analog-to-digital (A/D) converter.
Sensor systems with a given range of bias over temperature are typically calibrated for zero output stability by calibration over temperature in the analog domain prior to digitization. A more cost effective and stable way to do the calibration is to do it in the digital domain. However, in such systems, the dynamic range of the A/D converter has to be shared between the input signal and the offset variation, and the dynamic range of the calibrated signal is reduced.
One way to overcome the reduction in dynamic range is to reduce the analog scaling of the signal. However, that results in a lower signal-to-noise ratio and reduced resolution of the digital signal.
The reduction in resolution can be avoided-by using an A/D converter with higher resolution. While that will maintain or improve the resolution of the digital signal, it requires a more expensive A/D converter.
It is in general an object of the invention to provide a new and improved system and method for extending the dynamic range of an A/D converter.
Another object of the invention is to provide an improved system and method of the above character which overcome the limitations and disadvantages of the prior art.
These and other objects are achieved in accordance with the invention by providing a system and method for improving the dynamic range of an A/D converter in which operation the A/D converter is monitored, and an offset signal is combined with an analog input signal to maintain the operation of the A/D converter within the dynamic range.